Policy Bundling and Vote Choice in the United States
Political parties in the United States take divergent platforms on both economic and social issues, which
forces cross-pressured voters—those with preferences to the left on one dimension and the right on the
other—to suppress one dimension of conflict when voting. Using observational data and survey
experiments, we show that the introduction of a religious or moral values dimension has a large impact
on the choices of such voters. We find no evidence that the introduction of the social dimension
generates an asymmetric realignment in favor of one party or the other. Rather, the effect is symmetric
and driven by social extremists on both the right and left. These findings are at odds with the familiar
one-dimensional assumption in the American politics literature, and consistent with theories that look
to multi-dimensional politics for explanations of phenomena like political polarization.
Aina Gallego
Ramon y Cajal Fellow, Institut de Barcelona d’Estudis Internacionals
agallego@ibei.org
Jonathan Rodden
Department of Political Science, Stanford University
jrodden@stanford.edu
March 6, 2015
1
Introduction
While an economic dimension of partisan conflict over taxation and redistribution has been at
the heart of democratic politics at least since the rise of mass suffrage in most industrial democracies,
policy disagreements related to religion and moral values have continued to provide structure to
political conflict in many societies around the world, generating a cleavage that has consistently rivaled
social class over the last century (Caramani 2004; Dalton 2008; Elff 2007). In the United States, a large
literature tracks the recent revival of this dimension and its replacement of race as the second
dimension in U.S. politics (Ansolabehere, Rodden, and Snyder 2006; Baldassarri and Gelman 2008;
Layman 1997, 2001).
The United States stands out among advanced democracies for at least two reasons. First, the
raw material for a religious dimension of political conflict is more obvious in the United States than in
other wealthy democracies. While many Americans—especially in dense city centers and on the
coasts—have become as secular as Europeans in recent decades, the rest of the United States retains a
much larger concentration of highly religious and socially conservative individuals than can be found in
almost any other advanced industrial democracy.
Second, in spite of its heterogeneity and size, the United States has the purest two-party system
of any advanced industrial society. In a multi-party system like those produced by European-style
proportional representation, parties can more fully occupy a two-dimensional issue space, providing
alternatives for cross-pressured voters to find parties with proximate views on both dimensions. For
example, working-class advocates of the welfare state with morally conservative views can cast a vote
for Christian Democrats, while economic conservatives with morally progressive views can vote for a
Liberal or Libertarian party. By contrast, a strict two-party system in which economic and moral issues
are bundled together by the parties offers no such alternatives. A secular, high-income American
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supporter of gay rights who also favors lower taxes must choose between her preferences over gay
rights and those over taxation when choosing between Democratic and Republican presidential
candidates.
This paper is motivated by a classic question at the intersection of American and comparative
politics: to what extent does the American two-party system force voters to suppress their preferences
on one dimension in favor of the other? In other words, how might American electoral politics change if
a proportional electoral system suddenly produced the potential for a broader menu of choices that
might include a Libertarian or Christian Democratic option? We also ask a secondary question with
important implications for the study of American politics: which voters suppress which issue
dimension?
The American politics literature is divided on this topic. One prominent claim in the literature is
that cross-pressured voters are so few in number that American public opinion can be viewed as
effectively one-dimensional. Either the bundles adopted by the parties are very good reflections of the
underlying correlations of voters’ preferences, or voters have resolved cognitive dissonance over time
by bringing their preferences into line with the bundles offered by the parties. Because of the analytical
intractability of two-dimensional models of electoral competition (McKelvey 1976), scholars often adopt
and defend this one-dimensional representation of public opinion as a necessary simplifying assumption
that happily approximates the truth (Bafumi and Herron 2010; Jessee 2009; Shor and McCarty 2011;
Stimson 1991; Tausanovitch and Warshaw 2013). In this view, partisanship and ideology are essentially
the same concept. If this assumption indeed approximates reality, there is little underlying demand in
the electorate for parties offering alternative bundles of issues.
However, this perspective is challenged by a separate empirical literature that uses a variety of
techniques to demonstrate that the number of cross-pressured voters is actually quite large. For
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example, Poole and Rosenthal (1984), Zaller (1992), Treier and Hillygus (2009), Baldassarri and Goldberg
(2014), and Krasa and Polborn (2014) find that large numbers of American voters are to the right of the
overall median on social issues but to the left on economic issues (henceforth Christian Democrats), and
a roughly similar number can be characterized as falling on the social left and economic right
(henceforth Libertarians).
If these studies are correct, the current two-party system indeed forces many Americans to
suppress their preferences on one dimension or the other when casting a vote in national elections.
Because of the dominance of the one-dimensional assumption, the American politics literature provides
surprisingly little insight into how voters assign relative weights to the two dimensions when deciding
which to suppress. One possibility is that the weights are roughly the same across the entire electorate.
For instance, Bartels (2006), and Ansolabehere et al (2006) claim that voters across the ideological
spectrum consistently place far greater weight on the economic dimension. A second possibility,
consistent with the finding that issue extremity and importance tend to correlate (Ajzen 2001; Petty and
Krosnick 1995), is that social extremists on both the left and right assign relatively more weight to social
issues than social moderates when deciding for whom to vote. A third possibility is that there is an
asymmetry such that one group of cross-pressured voters—religious social conservatives according to
Thomas Frank (2004) or secular social progressives according to Andrew Gelman et al (2008)—places
greater relative weight on the social dimension.
Each of these perspectives leads to a rather different understanding of contemporary U.S.
politics, and a different interpretation of the rise of politicized religion that started in the 1980s. The
first two views imply that platform divergence on social issues encourages a symmetric realignment
whereby some socially progressive Republicans become Democrats and some socially conservative
Democrats become Republicans. In the second view, this realignment is driven primarily by those with
4
the most extreme social preferences. Alternatively, Thomas Frank (2004) famously describes an
asymmetric realignment in which the latter effect is larger than the former, generating a subtle longterm advantage for the economic right.
These arguments are rather loose in the existing empirical literature, which is often not clear
about the interplay of party platforms, the sizes of cross-pressured groups, and the relative weights
placed by voters on the two issue dimensions. The first task of this paper is to clarify these arguments in
a common theoretical framework. The second task is to apply this framework to several decades of
survey research, improving on the model-dependence of existing empirical studies by using a support
vector machine algorithm to reveal the dividing line between Democratic and Republican voters in U.S.
presidential elections. We show that a one-dimensional conflict over economic policy has indeed given
way to a two-dimensional conflict that includes social policy. Moreover, consistent with Miller and
Schofield (2003, 2008) there is some evidence that this realignment was initially driven
disproportionately by those with relatively extreme social preferences. We see no consistent evidence
of the kind of asymmetric realignment described by Frank (2004).
While the external validity of this observational approach to policy bundling is desirable, its
internal validity is extremely limited, above all because it provides neither control over the positions of
parties nor a clear counterfactual in which policies are unbundled. The central empirical contribution of
this paper is to present the results of survey experiments that manipulate candidate platforms and
contrast the choices of respondents under conditions of American-style policy-bundling—where only
two candidates take positions on both dimensions of conflict—with conditions where policies are
unbundled. One form of unbundling is akin to a situation in which the parties do not offer distinctive
platforms on the social or religious dimension, as in the United States in the 1970s. The other form of
5
unbundling is akin to a European-style system of proportional representation in which candidates offer a
wider range of platforms in the two-dimensional policy space.
Our findings demonstrate that the choices of cross-pressured voters are dramatically different
under conditions of policy bundling than when policies are unbundled. Religious moral conservatives as
well as secular moral leftists are willing to ignore their economic preferences when the moral issue
dimension is introduced. For both groups of voters, this effect appears to be driven disproportionately
by respondents with relatively extreme preferences on the moral values dimension. We interpret this as
evidence that extremists on the social dimension place greater weight on this dimension relative to the
economic dimension. This conclusion is bolstered by a separate analysis in which respondents with the
most extreme social views reported placing a greater weight on these issues relative to economic issues
when going to the polls. Finally, in neither type of analysis do we see consistent evidence of an
asymmetry of the kind implied by Frank (2004).
Taken together, the observational and experimental findings have potentially important
implications. Not only are cross-pressured voters numerous, but those with the most extreme social
preferences also appear to suppress their economic preferences. As suggested by Baldassarri and
Goldberg (2014), there are strong and consistent social liberals and social conservatives in the offdiagonals of a two-by-two matrix of social and economic preferences. In a proportional electoral
system, they would provide the impetus for party entry. In the United States, they are a thorn in the
side of the existing parties (Miller and Schofield 2003).
When scholars ignore these individuals in order to achieve analytical tractability, they turn a
blind eye to an important feature of electoral competition. The final section introduces the possibility
that cross-pressured voters are geographically concentrated, such that the introduction of the social
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dimension in the latter part of the 20th century contributed to regional realignments that reduced the
number of competitive districts.
The Effects of Policy Bundling
Let us begin by considering a scenario that captures basic features of the distribution of
preferences in many countries. Voters have preferences on two distinct policy dimensions—a primary
dimension rooted in conflicts over the government’s role in regulating the economy and redistributing
income, and a secondary dimension related to moral issues like women’s rights, homosexuality, and
abortion—and preferences on these two issue dimensions are positively but weakly correlated (de la O
and Rodden 2008).
Figure 1: Simple example of two-dimensional preference distribution: ANES 2008-2012
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To capture this, we have generated issue scales using multiple policy questions from the 2008
and 2012 versions of the American National Election Survey (see the appendix for details). The scales are
normalized to have mean zero and a standard deviation of 1. Figure 1 displays the moral scale on the
horizontal axis and the economic scale on the vertical axis. The scales are weakly correlated (around
.20). Around 58 percent of the population is not cross-pressured: they have preferences to the right or
left of the median on both dimensions. Henceforth, we refer to these on-diagonal voters as “right wing”
and “left wing.” The remaining 42 percent of the population has preferences either to the left of the
economic median and to the right of the moral median (Christian Democrats), or to the right of the
economic median but to the left of the moral median (Libertarians).
Let us first consider a scenario in which only the economic dimension is politicized. In Panel A of
Figure 2, two candidates, c1 and c2, set their platforms symmetrically around the median voter on the
economic dimension, but they are perceived as offering identical platforms directly at the median on the
moral values dimension. This example represents a situation in which the non-economic dimension is
not politicized, and neither party is proposing any significant change to the status quo. This is the
standard description of American politics prior to the politicization of issues like abortion, religious
freedom, and gay rights. It also corresponds to relatively secular countries like Great Britain and the
Nordic countries, where party conflict has little to do with issues like abortion and gay rights.
Let us consider a simple model of vote choice in which these platforms are first exogenously
determined by the candidates, , and then voters simply choose the most proximate candidate in the
two-dimensional Euclidean issue space. By the Pythagorean Theorem, this amounts to the following
decision rule for voters:
(1)
8
where
and
are the economic and moral platforms of each candidate j, and
and
are the
economic and moral preferences of the voter i. Thus in Figure 2A, all voters above the economic median
vote for the party of the right (represented in red), and all voters below the economic median vote for
the left (represented in blue), regardless of their moral views. In this example, the isoprobability
frontier—where voters are indifferent between the candidate of the left and right—is simply a
horizontal line at the median economic preference.
Figure 2: Hypothetical candidates and voter weights
Next, let us consider what happens when the second dimension is activated. This might happen
because parties react to an exogenous shock that changes the status quo, like the Roe versus Wade
Supreme Court decision, or because parties strategically undertake the “flanking” maneuvers described
by Miller and Schofield (2003). In their model, each party’s perceived platform is a function of the policy
9
interests of its activist core of campaign contributors. Office-oriented candidates ascertain opportunities
to gain disaffected activists in the off-diagonals by offering them policy concessions, bringing them into
their group of core activists, and hence changing the party’s perceived platform. Ultimately this flanking
maneuver leaves the party exposed, inviting a symmetric move by the other party.
In Panel B of Figure 2, a flanking move of this kind is portrayed: both candidates keep their
economic positions the same, but c1 moves .5 of a standard deviation to the moral right and c2 moves
symmetrically to the moral left. For the voters in each of the off-diagonals, the improved proximity on
the moral dimension causes some of the voters to switch to the opposite candidate. The isoprobability
frontier separating the voters of the right and left parties has now shifted from horizontal to diagonal.
This account of the rise of multi-dimensional competition captures the standard accounts in the
literature, such as those of Miller and Schofield (2003) or Krasa and Polborn (2014), where diverging
candidate platforms on the second issue dimension cause a rotation in the isoprobability frontier,
conceived as a straight line.
However, it is possible that the divergence of candidate platforms on the moral issue dimension
is not especially consequential if voters attach far less weight to those issues (Bartels 2006). Let us
consider the term
, capturing the relative weight placed by each respondent on economic versus
moral issues, which changes the voter’s decision rule as follows:
(2)
In this formulation, if
is sufficiently large (small), a cross-pressured voter will choose the party that is
more distant in Euclidian space because she gives greater weight to the moral (economic) dimension. If
everyone has
=0, the isoprobability line would not change no matter how much the candidates diverge
on the moral dimension. If everyone has
=.5, the isoprobablility frontier shifts as a straight line when
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candidates diverge on the moral values dimension. However, the indifference curve of an individual with
becomes increasingly ellipsoidal in a vertical direction as
gets larger and the relative
importance of proximity on the moral values dimension increases. For an individual with
, the
indifference curve becomes increasingly ellipsoidal in a horizontal direction as she becomes relatively
less willing to accept compromise on the economic dimension.
We interpret the classic Marxist story about religion, as famously applied to the American
context by Thomas Frank (2004) as an assertion that it induces a positive correlation between
and
. In other words, more religiosity is correlated not only with increasingly right-wing preferences on
the non-economic policy dimension, but also with a greater weight on that dimension—a decreasing
willingness to sacrifice sacred for secular preferences.1 This hypothesis is consistent with recent
psychological literature demonstrating that many religious individuals have a distinctive approach to
morality, favoring a non-consequentialist logic whereby there is a class of sacred moral values that
should never be sacrificed in favor of secular goods like monetary gain (Piazza and Sousa 2014; Tetlock
2003).
Let us now examine a situation in which the candidates occupy the same positions as in Figure
2B, but now the voters are weighting the policy distances by
that is perfectly correlated with
. In
Figure 2C, we see that this has a dramatic effect. Because they place larger weight on moral values,
many Christian Democrats now prefer c1 because of its proximity on the moral values dimension.
1
Note that this version of the Marxist argument is distinctive from that of Roemer (1998), where policy-bundling
generates an asymmetric push against the preferences of the economic left because of a specific feature of the
joint distribution of preferences on the two dimensions. In Roemer’s model, economic preferences are perfectly
correlated with income. Reflecting the interests of its core constituents, the party of the left would push for
radical redistribution in the absence of a bundled non-economic issue dimension. However, if the voters around
the median level of religiosity have above-average income, the party of the left would offer a lower tax rate and a
less redistributive policy agenda as it attempts to win support among anti-clerical high-income voters.
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Because they place greater weight on economics, the vast majority of Libertarians also now prefer the
party of the right.
In this scenario the isoprobability frontier is no longer a straight line, but a curve that paints the
leftist party into a corner. This is a troubling scenario for the party of the left: political competition is
shifted to the economic right of where it would be in the absence of candidate divergence on the
second dimension or the absence of a correlated
party of the right if
. Of course the same phenomenon would plague the
were negatively correlated with preferences on the moral dimension, such that
secular voters would disproportionately abandon the party of the right upon introducing the moral
values dimension (Gelman et al 2008: 88-93).
A third possibility is that
displays a U-shaped relationship with moral values preferences, such
that it takes on low values among moral moderates, but increases symmetrically as voters become more
extreme. This possibility is consistent with the finding that people who hold extreme opinions on an
issue are also much more likely to consider these opinions as personally important (Ajzen 2001, Krosnick
and Petty 1995). If extremely religious people place higher weight on the moral values dimension
because it touches on deeply held moral principles that cannot easily be subjected to trade-offs,
perhaps the same is true for extremists on the moral left who view abortion, gender equality, and gay
marriage as fundamental rights that are more important than economics. Consistent with this view,
strong Republicans and strong Democrats are equally likely to report in surveys that their views on
abortion or same-sex marriage reflect deeply held moral convictions (Ryan 2014). This u-shaped
relationship is also built into the assumptions of the two-dimensional models of Schofield (see, e.g.
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Schofield 2008), where the activists pushing the parties to adopt divergent policy platforms on the social
dimension are social extremists with ellipsoidal indifference curves.2
In Panel D of Figure 2, we consider a case in which the relationship between α and moral
preferences has a parabolic shape, such that moral extremists of both the left and right place greater
relative weight on the moral dimension and moderates give it a weight approaching zero. In this case,
the isoprobability frontier takes an S shape, with the party of the right gaining ground especially among
the most morally conservative Christian Democrats, and the party of the left gaining ground especially
among the most morally progressive Libertarians.
Observational research in the United States
There is little disagreement that the platforms of the two major American parties have diverged
significantly since the 1980s, as depicted in the examples above. But there is little agreement about
what this means for U.S. or comparative politics. In a European-style system of proportional
representation, a similar constellation of political preferences would likely facilitate the emergence of a
2
Of course, a similar argument could be made about the existence of a u-shaped relationship between alpha and
economic preferences. This possibility is somewhat less plausible. The relative importance of one issue dimension
should depend on how strongly connected a position is to deeply held values. For moral extremists, even small
concessions on an issue like abortion may amount to violating a core, untradeable value such as the sacredness of
life or the freedom of choice over one’s body. People who hold such principled views, associated with extremists
rather than moderates, may be particularly unwilling to trade off concessions on the moral dimension for wins in
other areas, resulting in a high alpha. The situation is different for economic extremists. Extreme economic
proposals, such as a complete elimination of all markets or of all economic regulation, are not often connected to
similar types of untradeable sacred values and these radical policies can be viewed as dangerous and leading to
economic collapse. Economic moderates should attach a high importance on having moderate economic policies
on the grounds of avoiding large risks. Besides these theoretical speculations, we have extensively explored the
correlation between alpha and economic extremism empirically and address this issue in the supporting
information. The results strongly suggest that economic moderates and extremists place a similar importance on
both issue dimensions. For both theoretical and empirical reasons, the rest of the paper assumes that alpha is
constant across economic issue positions.
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more than two parties to fill up the two-dimensional space (Ordeshook and Shvetsova 1994, Neto and
Cox 1997, and Cox 1997), which would absolve voters of the need to choose between their economic
and non-economic preferences (De la O and Rodden 2008, Huber and Stanig 2009). In the United
States, however, the strict two-party system forces cross-pressured voters to make a difficult choice,
and we know rather little about how they do so.
One reason for this is the dominant claim in the American politics literature that there is only
one relevant dimension of political conflict. This perspective is often invoked as a simplifying
assumption, but it is also defended by the application of dimension-reduction techniques such as itemresponse-theory (IRT) models to large numbers of policy-related survey responses of voters or all
Congressional roll-call votes. A common technique is to calculate the percent of responses or votes
correctly predicted by the first dimension, and then conclude that the data are “one dimensional” if this
success rate does not improve a great deal with the addition of the second dimension (Jessee 2009,
Tausanovitch and Warshaw 2013, Poole and Rosenthal 2007).
Such demonstrations of unidimensionality have been called into question in recent literature.
Ahler and Boockman (2014) show that dimension-reduction techniques applied to binary survey
responses can easily misclassify cross-pressured voters as moderates. Aldrich, Montgomery, and Sparks
(2014) show that partisan polarization might create a false appearance of one dimension using this
approach, and several scholars have pointed out that very few divisive social issues reach the floor for a
vote because party gatekeepers keep them off the agenda when the party is not unified (e.g. Snyder
1992, Harbridge 2015). More generally, inferences drawn from this approach are greatly influenced by
the number and quality of survey questions (or roll-call votes) on different issues: if there are few good
questions about moral values and many economic questions, it would not be surprising to find that a
second dimension fails to increase the number of correctly predicted items. This approach might also
14
lead to questionable inferences about the dimensionality of the data if measurement error varies with
the substance of the questions.
Instead of examining the first and second dimension of a model that includes all survey
questions or votes, an alternative approach is the one introduced in Figures 1 and 2 above: the
researcher can use theory and contextual knowledge of political debates to select clusters of items to
include in issue-specific scales, and examine whether a multi-dimensional structure is helpful in
explaining voting patterns. Several papers apply this approach and find that the correlation between
moral and economic preferences is relatively low, and examine whether the divergence of party
platforms on the moral dimension has led to a shift in the isoprobability frontier from horizontal to
diagonal (Feldman and Johnston 2014, Ansolabehere et al 2006, Bartels 2006, Baldassarri and Goldberg
2014, Krasa and Polborn 2014).
With the exception of Baldassarri and Goldberg (2014), these papers conceive of the
isoprobability frontier as a straight line, and do not adopt flexible modeling strategies that might
unearth the possible kinks in the frontier described above. Instead of relying on regression analysis, we
use a support vector machine (SVM), a global classification model that generates a non-overlapping
partition of the two-dimensional space according to presidential vote choice based on maximum
marginal linear discriminants. That is, the SVM classifier chooses the hyperplane with the maximum
margin between Democrats and Republicans. The resulting partition line between the predominantly
Democratic and Republican surfaces is our estimate of the isoprobability lines.
We apply the SVM classifiers to two different datasets: the American National Election Studies
(ANES) and the General Social Survey (GSS). Both studies cover the period in which the moral platforms
of the parties diverged and contain many questions about issue positions asked in identical terms across
multiple waves. The ANES is specifically designed to study electoral behavior and asks about presidential
15
vote just after each election, hence facilitating more accurate recall. On the other hand, we are only able
to generate consistent issue scales between 1984 and 2012, and the number of observations is smaller
than for the GSS.3 Recall of presidential votes may be less accurate in the GSS, which is conducted long
after each election, but this dataset has important advantages. First, we are able to create consistent
scales for a somewhat longer period stretching between 1976 and 2008, and second, the number of
observations is also more than twice as large as in the ANES because we pool responses to the multiple
waves conducted between presidential elections. More cases allow for a more accurate examination of
the shifts in the isoprobability lines in the sparsely populated areas of cross-pressured and extremist
voters. Because the hypotheses differ precisely about the predicted patterns in these areas, the GSS
may overall be the most appropriate dataset for this analysis.
We create issue scales with multiple items in order to reduce measurement error. The criteria to
include the items are threefold. First, the items must tap into the core substantive content of the
economic and moral dimensions as commonly defined in previous studies about issue dimensions in the
US (Baldassarri and Goldberg 2014; Feldman and Johnston 2014; Treier and Hillygus 2009). For instance,
the economic issue scales include questions about redistribution, the role of government, or public
spending, but not about foreign policy. Second, the scales only include questions asked in most of the
waves. And third, the questions must exhibit at least moderate correlations with the other items in the
scales.4
3
The number of identical questions declines dramatically before 1984 casting doubt on the validity of longitudinal
comparisons. The number of cases is also more limited because we only use the surveys conducted in presidential
years. While we could include the surveys conducted in midterm election years, this does not result in a large
increase in the number of observations because only some of the waves (1990, 1994, and 1998) ask about recall of
the vote in the last presidential elections. The results do not change significantly when we add those cases and, in
any case, this approach does not allow us to explore in more detail the shifts in the isoprobability lines in the
period of realignment before the 1990s, which is the most relevant for us.
4
The supporting information and replication files document the relevant decisions taken when constructing the
scales and provides details about the questions, the measurement models, the properties of the scales, and
16
This content-driven approach to the creation of scales is well-suited to the task at hand: if the
null hypothesis that the moral issue dimension has a negligible importance on vote choice is true (hence
alpha is close to 0 and politics is basically unidimensional), then we would expect a flat horizontal line
over the whole period when using these or any other scales. In addition to establishing whether the
isoprobability line indeed shifts over time, we are interested in specific changes in its shape.
Figures 3 and 4 display the evolution of the shape of the isoprobability lines over time for the
ANES and the GSS respectively.
number of observations. In table A1 in the supporting information we also discuss the main differences in the
socio-demographic and political profiles of respondents in the four quadrants. Christian Democrats stand out from
all other groups for their low level of education and income and their low voter turnout rates. They are the most
ethnically diverse group and are similar to right-wing respondents in their religious profiles. Libertarians are the
most highly educated group and the least likely to attend church.
17
Figure 3: Isoprobability lines in the American National Election Studies 1980-2012
18
Figure 4: Isoprobability lines in the General Social Survey 1976-2008
In both datasets, we observe a clear shift from a more horizontal to a diagonal isoprobability
line over time. The shift started in the 1980s, during the period that is widely acknowledged to have
seen the rise in importance of moral issues. The results need to be interpreted cautiously because we do
not measure the exact location of party platforms and the shift could conceivably be attributed to other
changes occurred during the period. Still, the pattern is very consistent with the claim that as positions
on the moral issue dimension diverged, a sizable number of cross-pressured respondents became more
likely to vote against their economic preferences and switch to the party with a congruent position on
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moral issues. This evidence disconfirms the unidimensional view of politics in presidential elections:
both dimensions seem to matter for voters in the later period.
After ruling out the one-dimensional view, we next examine the precise shape of the
isoprobability line during and after the rise of moral issues. The line should be c-shaped (facing
downwards or upwards) if alpha is correlated with moral conservatism or liberalism, implying that either
the Democrats or the Republicans disproportionately benefit from the realignment. Alternatively, the
shift could lead to symmetric wins and losses of cross-pressured voters for both camps if the relative
importance of moral issues, or alpha, is either constant across individuals, in which case we would
expect a straight diagonal line, or is correlated with moral extremism, producing an s-shape.
The results are strongly consistent with the latter account, and disconfirm the first. In the GSS,
which has a larger number of respondents and allows for more accurate observation of changes in the
off-diagonals, we see clear s-shaped lines in 1984 and 1988, precisely during the critical rise of moral
issues in national political debate. This finding is consistent with the notion that the realignment of the
US party system was initially driven by activist extremists. In most of the rest of the plots the line is
diagonal, with waves but no dominant pattern. With some possible exceptions, and in particular 1992 in
the ANES, overall the evidence does not support any of the two versions of narratives in which the
importance of moral issues is asymmetric, either because Christian Democrats (Frank 2004) or
Libertarians (Gelman 2008) value proximity on moral issues relatively more than voters in the opposite
quadrant.
The observational data point to an important transformation of American electoral politics, but
it is difficult to know what exactly lies behind it. Importantly, we cannot know with certainty whether
the shift can be attributed to the divergence in party platforms over time, or to a change in the weights
placed by voters on the social relative to the economic dimension. Previous observational studies also
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fail to distinguish between both possibilities. In fact, Krasa and Polborn (2014) simply use the relative
predictive power of economic preferences vs. religiosity in a model of vote choice as proxies for
platform divergence, assuming away the issue of weights. Bartels (2006) and Ansolabehere et al (2006),
on the other hand, treats coefficients on issue scales in simple vote choice models as proxies for
weights. In any case, voter weights and perceptions of platform divergence both plausibly shape one
another, and are mutually shaped by long-term trends like secularization and the women’s movement
and shocks like the Roe versus Wade decision. Observational data, moreover, do not allow identifying
the effect of the introduction of the moral issue dimension on vote choices because multiple non-issue
considerations (including valence considerations or candidate’s attractiveness) vary from election to
election and may correlate with issue positions and other individual characteristics. In other words,
omitted variables possibly shape the form of the cutoff lines.
Candidates experiments
The remainder of this paper attempts to cut through this thicket by gaining experimental
control over party platforms through the use of hypothetical candidates rather than attempting to
characterize voters’ perceptions of relative platform divergence as they unfold across decades. Our goal
is to enable causal inferences about the effect of divergence between candidates on moral issues.
Generating unbundled counterfactuals and contrasting them with a scenario that captures the
contemporary U.S. party system allows us to draw inferences about voters’ weights that cannot emerge
from the analysis of observational data.
Design and procedures
The experiments asked respondents to vote for hypothetical candidates and manipulated the
menu of choices such that we can compare the vote choices of citizens in a policy bundling situation, in
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which two candidates differ on both economic and moral issues, and their choices in other situations
that, by design, do not require cross-pressured citizens to engage in a trade-off between their economic
and moral issue positions. Comparing vote choices in the presence or absence of policy bundling allows
us to assess if introducing moral issues in a two-party system leads some cross-pressured respondents
to vote for candidates who do not hold their most preferred economic platform, and if this switch is
more pronounced for some voters than others.
We embedded the experiments in two online surveys fielded by SSI, a polling company, in June
2013 and July 2014. In total, 1619 respondents completed the first survey and 909 completed the
second. The supporting information provides details of the studies.5
The experiments have four treatment conditions. The first two conditions describe candidates
with positions on only one dimension, allowing us to elicit the baseline support for each camp in a onedimensional issue space. In treatment (1), the economics only condition for brevity, the two candidates
differ only on economic issues, a situation akin to our characterization of American presidential
elections prior to the Reagan era. In treatment (2), the morals only condition, they differ only on moral
issues.6 In treatments (3) and (4) candidates have positions on economic and moral issues. Treatment
(3), the policy bundling condition, describes two candidates with congruent positions on economic and
5
The sample, while similar to the population in terms of socio-demographic characteristics, is more left-leaning
than the population, as is usual in online surveys. The left skew was larger in the second study compared to the
first study. Table A2 in the supporting information reports the distribution of key political variables such as partisan
identification, ideology, or attitudes towards abortion in the two studies and the 2012 American National Election
Study. The samples, especially the second, are also less religious than comparable samples, but the difference is
not large.
6
While it can be argued that respondents may have attributed other characteristics to the candidates when
learning about their issue positions, such as partisanship or positions on other issues, we attempted to avoid
projection of non-issue considerations by emphasizing that the candidates were hypothetical, had otherwise
similar positions on all major platforms and issues, and did not belong to a party (e.g. Tomz and Van Houweling
2008, 2009)Specifically, all participants were told: “We would like to know your opinion about two [four]
candidates. They have similar platforms on all major political issues except for the positions we describe below.
The description is general, and is not about candidates from a specific party. Which candidate do you prefer?”
22
moral issues. This is the only treatment that forces cross-pressured respondents to suppress their
preferences on one dimension and the situation that most resembles the current political system in the
United States. Treatment (4), the unbundled condition, frees respondents of forced choice in a twodimensional issue space by providing four candidates occupying all quadrants. It is akin to our
characterization of European proportional representation. After reading the descriptions, respondents
were asked to choose one of the candidates, and they did not have the option of abstaining.
To recapitulate, in the absence of policy bundling, cross-pressured individuals should choose the
closest candidate on the economic dimension. That is, Christian Democrats will prefer economically leftwing candidates and Libertarians will vote for right-wing candidates when competition is only about
economic issues as well as in a four-candidate situation. We ask if policy bundling causes a sizeable
number of cross-pressured respondents to vote for an economically distant candidate. We are
interested in two comparisons.7 The first is the vote for the economically right-wing candidate in the
baseline economics only situation and in the policy bundling situation. This difference addresses the
question: How do voters’ choices in a two party system change following the introduction of debate on
moral issues? We also compare vote choices in the policy bundling and unbundled conditions and
address the counter-factual: How would the choices of American voters change after the sudden
introduction of a broader menu of choices?
The economic positions of candidates describe their views on social spending and taxes, while
the moral issue positions are views on abortion and same-sex marriage. Previous research suggests that
these issues are the most important markers of economic and moral attitudes in the US (Treier and
Hillygus 2009).
7
Including the condition with two candidates with only positions on moral issues is necessary for design purposes,
but here we focus on the analysis of the differences between the three conditions of more analytical interest.
23
We used a different description of economic positions in the two experiments, which produced
large changes in the choices of respondents. In the first experiment, the wording was: “Candidate [A/B]:
Wants [less/more] spending on social programs and [lower/higher] taxes for wealthy citizens.” The
supporting information shows an example of how respondents encountered the information. A large
majority of respondents (73 percent) chose the economically left-wing candidate in the economics only
condition. In order to compensate for this skew, and to assess the robustness of the results to a
different location of the candidates in the economic issue space, the second experiment modified the
question wording, proposing tax changes for all citizens rather than only for the rich: “Candidate [A/B]:
Wants [lower/higher] taxes and [less/more] spending on social programs.” This time, only 35 percent of
respondents chose the economically left-wing candidate.
Having one study with the left-wing candidate perceived as centrist on economic issues and the
other study with this candidate perceived at the extreme left (and corresponding changes for the rightwing candidate) is useful because it allows us to focus, in each experiment, on a different group of crosspressured respondents: In the first experiment, the placement of the candidates situates a majority of
respondents to the left of the mid-point between the candidates on economic issues, resulting in a large
number of cross-pressured moral conservatives with left-wing preferences. In the second experiment, a
majority of respondents are economically right of center relative to the midpoint between the
candidates, generating many cross-pressured Libertarians.
In both experiments, the moral issue positions were described as follows: “Candidate [A/B]:
Wants [more/fewer] restrictions on abortion and [a ban on/legal] same-sex marriage.” In the first
experiment, 52 percent of respondents voted for the left-wing candidate in the morals only condition,
but this figure rose to 62 percent in the second. The difference may be due in part to sampling variability
and to the somewhat more morally liberal views of the latter sample (see supporting information).
24
Unfortunately, the combination of the two skews in the second experiment, along with the smaller total
number of cases, leaves us with very few cross-pressured Christian Democrats and impedes making
inferences about their choices.
For these reasons, the analysis of the first experiment concentrates on the reactions of Christian
Democrats while the analysis of the second experiment focuses on Libertarians.
The studies also contained information about respondents’ background and political views. To
situate respondents on economic issues we estimate latent scores based on three questions about
redistribution, unemployment benefits, and taxes.8 The measure of moral issue positions is the latent
score of three questions about abortion, same-sex marriage, and adoption by same-sex couples. Higher
values of the variables stand for morally conservative views.
Results
Table 1 reports the share of the vote for each candidate in each condition for the two
experiments.
8
We use a standard structural equation measurement model. As discussed in the supporting information, we
regard this approach as preferable to IRT given the nature of the latent variables and the response options of our
scales. The results are robust to using other methods to extract the latent scores of economic and moral
conservatism, such as factor analysis, principal component analysis, and generalized structural equation models.
The correlations between the measures are always larger than 0.95. In the first experiment, the reliability
coefficients were 0.55 for the economic scale and 0.66 for the moral scale. In the second experiment, the values
were 0.61 and 0.74 respectively. The supporting information provides further details about the questions. The first
experiment contained a larger number of issue questions. The results are substantively the same when we
estimate economic and moral positions using a larger number of items. We present the results based on scales
constructed using the same items in order to maximize comparability across the two studies.
25
Table 1: Vote choice across treatment conditions
First experiment
Second experiment
Economics only
Economically left-wing
73
35
Economically right-wing
27
65
Morals only
Morally left-wing
52
62
Morally right-wing
48
38
Policy bundling
Left-wing on both dimensions
63
48
Right-wing on both dimensions
37
52
Unbundled
Left-wing on both dimensions
46
25
Right-wing on both dimensions
18
35
Christian Democrat
27
7
Libertarian
9
33
Number of observations
1619
909
We observe large changes in support for the candidates in the policy bundling condition relative
to the baseline conditions in both studies, providing preliminary evidence that voters are highly
responsive to the introduction of moral issues in a two-candidate situation. Support for the
economically conservative candidate is 10 percent points higher in the policy bundling condition than in
the economics only condition in the first experiment and the difference is statistically significant
(p=0.002). The 13 percent points difference in the second experiment is also significant (p=0.006). These
findings should not be interpreted as evidence consistent with asymmetric effects because the results
are shaped by ceiling effects. In the first experiment, a large share of respondents chose the candidate
of the economic left in the baseline condition and the introduction of moral issues had more room to
reduce the vote for that candidate. The opposite is true in the second experiment.
Next we turn to assessing heterogeneous treatment effects and ask: Does policy bundling cause
cross-pressured respondents to disregard proximity on economic issues and vote for the candidate that
is closer on moral issues? We expect consistently left- and right-wing respondents to be largely
unaffected by the treatment. Because they are not cross-pressured, the introduction of a congruent
26
second dimensions should not change their votes. The focus of interest is on the reactions of crosspressured respondents.
In order to identify cross-pressured voters, we first subset the sample between economically
left- and right-wing voters. Our preferred method of classification uses the economic position at which
respondents are indifferent between the two candidates as the cut-point.9 Economically liberal
respondents thus defined (80 percent of the sample in the first experiment and 24 in the second) are
voters who are more likely to vote for the left-wing candidate in the baseline situation.10 After subsetting by economic orientation, we plot vote choices and treatment effects against the continuous
measure of moral issues to explore differences between more moderate and extreme positions.
Before estimating treatment effects, Figure 8 presents the raw data and plots the average
proportion of respondents who vote for the economically left-wing candidate at different moral
positions in the three relevant experimental conditions. Cross-pressured Christian Democrats are at the
right end of the left panel. Libertarians are at the left side of the right panel.
9
In order to find the position in which respondents have an equal probability of voting for each candidate, we
regress vote for the candidates in the economics only condition on voters’ economic issues score. We estimate
that the probability of voting for each candidate equals 0.5 at the value 0.86 in the economic issue scale in the first
experiment and at -0.56 in the second. These values are the cut-points, and they are similar when using the results
of the unbundled condition. The distribution of the economic issue scales in both experiments is approximately
normal with a light right skew.
10
If we repeat the same classification in the moral dimension, hence dividing respondents in four quadrants, we
find that a substantial share of respondents (37 percent) experiences cross-pressures. This figure is similar to the
estimates of previous research using different criteria. For instance, in the National Election Study data presented
above, around 40 percent of U.S. citizens are cross-pressured. The estimate of Treier and Hillygus (2009) is
between 35 and 40 percent, Feldman and Johnston (2014) put the figure between 23 and 60 percent, and
Baldassarri and Goldberg (2014) found that 41 percent are cross-pressured. We assessed the validity of the
classification by examining the vote choices of the four types of respondents in the experimental condition with
four candidates, which allowed expressing their true preferences. In the first experiment, a plurality of voters in all
quadrants chose the closest candidate. In the second experiment, this is true for all quadrants except for crosspressured Christian Democrats. Unexpectedly, a majority vote for the candidate with left-wing positions on both
dimensions in the unbundled condition.
27
Note: The lines are the proportion voting for the economically left-wing candidate at different values of moral issue positions, estimated using
lowess smoothers. The data is subsetted by respondents’ economic position and treatment condition. The triangles display the location of
respondents on moral issues and their vote choices.
Figure 5: Vote choice by issue orientation across treatment conditions
As expected, non-cross-pressured respondents make similar choices in all conditions.
Respondents with left-of-center preferences on both issues (situated at the left side of the left panel)
always voted for the economically leftist candidate in very high numbers. Consistently right-wing
respondents (right extreme of the right panel) also voted for the economically conservative candidate at
similar numbers in all treatment conditions. By contrast, both cross-pressured groups exhibit very
different behavior across conditions, suggesting that they are strongly responsive to moral issues.
Relative to situations where they can express their economic preferences unconstrained, either because
28
competition is only about economic issues or because there are candidates in all quadrants, many crosspressured voters change their vote under policy bundling.
In the first experiment, all economically liberal respondents vote at high rates for economically
left-wing candidates when not forced to choose, but we observe in the policy bundling condition a steep
gradient: vote for that candidate declines as respondents become more morally conservative. Christian
Democrats make very different choices across conditions, implying that they care intensely about moral
issues.11 While the number of cases is smaller, we observe the opposite effect for Libertarians: many
shift to the left-wing candidate in the policy bundling situation. For Libertarians, the line is somewhat
curved, perhaps consistent with a stronger importance of moral issues among moral extremists.
The second experiment, which allows us to focus on Libertarians, confirms that they too are
willing to vote against their economic preferences in a policy bundling situation at high rates, even if
they overwhelmingly prefer economically right-wing candidates in the situations with no forced choice.
The large difference is visible in the left side of the bottom right panel. The only unexpected result is the
lack of a treatment effect among cross-pressured Christian Democrats in the second experiment. As the
plots suggest, the number of Christian Democrats is extremely sparse, and hence the pattern is driven
by very few cases.
Next, we estimate treatment effects. For simplicity, we focus on only one comparison, between
the economics only situation, which we define as the control condition, and the policy bundling
situation, the treatment.12 The treatment effect is the effect of learning about the candidate’s moral
views on vote choice in a two-candidate system. Assuming ignorability of treatment assignment, granted
11
This pattern holds for both Catholic and Protestant respondents, who exhibit very similar behavior across
treatment conditions.
12
As the raw data suggests, the pattern is largely the same when defining the unbundled situation as the
treatment.
29
by the experimental design, allows for identification of the full marginal distributions of the control and
the treatment outcomes at different values of the moral issue scales (Imbens 2004). We also assume
smoothness in the regression function of the outcome on the treatment, which seems to hold as
observed in Figure 5.
To estimate the treatment effects at different moral positions, we fit a logistic regression model
predicting vote choice with the treatment, the respondent’s moral issue positions, modeled curvilinearly
to allow flexibility,13 and the interaction between the two. The estimator is the average difference in
vote for the left for the treated units (in the policy bundling condition) and the controls (in the
economics only condition) at different values of moral issues. Again, we separate economically liberal
and conservative respondents. Figure 6 provides the point estimates and confidence intervals of the
treatment effects.
13
Using higher order polynomials yields substantively identical results. As suggested from an assessment of figure
5, the results do not change when using a matching estimator of treatment effects.
30
Note: The figures present the difference in the predicted probability of voting for the economically left-wing candidate in the policy bundling
condition (treatment) and the economics only condition (control) at different moral issue positions. The data is subsetted by respondents’
economic position.
Figure 6: The effects of introducing a moral dimension of electoral competition on vote choice
The results confirm the conclusions of the previous analysis. First, in both conditions, crosspressured Libertarians respond to the treatment by shifting to the economically left-wing candidate.
This effect is clearer in the second experiment, but the difference is also large and statistically significant
at high values of moral liberalism in the first experiment, where learning about moral issues causes a 40
percentage point increase in the predicted probability of voting for the left-wing candidate among
Libertarians with moral issue positions one standard deviation below the mean.
31
For Christian Democrats, we observe a substantively large and statistically significant treatment
effect in the first experiment. The treatment increases the probability of voting for the right-wing
candidate by 30 percentage points or more among those with moral issue positions one standard
deviation more conservative than the mean. In the second experiment, we do not observe a treatment
effect, which may be due to the reasons discussed above. However, the point estimates are on average
negative, as expected.14
Overall, the results confirm that learning about moral issues can lead to very large changes in
the vote choices of cross-pressured respondents, clearly disconfirming the unidimensional view of
politics. Second, the finding of large treatment effects among both groups of cross-pressured voters is
inconsistent with the hypothesis of asymmetric effects as postulated most famously by Thomas Frank.
Both strongly cross-pressured Christian Democrats and Libertarians change their votes at high rates
under policy bundling. Congruent with the results of the observational data, the experimental evidence
suggests that the introduction of moral issues leads to a realignment that is largely symmetric for both
camps. This effect is clearly driven by moral extremists, for whom the spatial distance between
themselves and the hypothetical candidate with the opposing moral platform is presumably largest.
Because the questions and platforms are not on the same scale, we are not in a position to uncover
individual values of alpha in order to examine whether they are constant across moral positions or
relatively larger for moral extremists. We turn to this question in the final analysis.
The self-reported relative importance of issues for moral moderates and extremists
14
Although not statistically significant, the point estimates suggest that the treatment reduces vote for the left by
about 15 percentage points at mid levels of moral conservatism (between 0.5 and 1 standard deviation above the
mean). The null results seem to be driven by very conservative cross-pressured respondents, which constitute a
very small group.
32
In the second survey, we asked respondents to directly assess the relative importance of
proximity on economic and moral issues when deciding for whom to vote. The wording was: “When
deciding for whom to vote, which is more important for you: the positions of candidates on economic
issues (such as taxes and services) or their positions on social issues (such as abortion and gay
marriage)?” Respondents were offered seven response options ranging from “Only economic issues are
important” (scored as 1) to “Only social issues are important” (scored as 7). This measure is a self-report
of alpha, the individual-level relative weight of economic and moral issues. Larger values imply a larger
relative weight of the latter. Figure 10 presents the average responses to this question at different
values of the moral issues scale.
Figure 7: Self-reported relative importance of issues
The results line up neatly with the observational and the experimental data. First, the selfreports of alpha once more disconfirm the claim that moral issues are unimportant for American voters.
In fact, a majority of respondents (51 percent) reports that both issues dimensions are equally important
when deciding for whom to vote. When one dimension is more important, it is largely the economic
33
one: The second most frequent answer is that “economic issues are considerably more important,”
chosen by 24 percent of respondents. Second, we find neither the asymmetry predicted by the Marxist
story nor its opposite. It is not the case that morally conservative religious individuals are more likely to
report that they care more about moral issues than do morally liberal secular individuals. The same ushaped pattern emerges when plotting responses against levels of religiosity . Third, the results once
again suggest that moral issues have a similar importance for both camps, consistent with the view that
their introduction may have lead to a symmetric realignment.
Finally, this is the analysis that most directly allows us to adjudicate between the claim that
alpha is constant across moral issue positions or it is larger among extremists. The pattern of responses
is clearly curvilinear. On average, respondents with very liberal and very conservative moral views report
that they care equally about both dimensions. At more moderate moral positions, respondents report
that economic issues are relatively more important than moral issues when deciding for whom to vote.
This suggests that alpha is u-shaped: Moral issues are relatively more important for moral extremists. 15
Discussion and Conclusions
We have presented results of two survey experiments that cast doubt upon the conjecture that
a single economic dimension is enough to capture electoral competition in the United States. Our main
finding is that the introduction of a bundled set of policy platforms related to moral values leads large
numbers of cross-pressured individuals to abandon their favored candidate on the economic dimension
(and vice-versa). Such cross-pressured voters can be found in large numbers in our surveys as well as
15
The supporting information provides more detailed analyses, which examine the correlation between selfreported alpha and economic and moral issue positions in a multivariate framework. The results reinforce the
conclusions of the bivariate analysis.
34
other larger, more representative surveys like the ANES. At least in our online samples, there is no
evidence for the conjecture that voters place zero or very low weight on moral issues relative to
economic issues.
We also examined the popular Marxist claim that moral conservatives place greater weight on
the non-economic dimension of conflict than do moral liberals, but our results were ambiguous at best.
In one experiment, the cut-points produced by respondents’ perceptions of the hypothetical candidates
gave us an ideal scenario for examining cross-pressured moral conservatives. In this experiment, the
treatment effect was much larger for moral conservatives. However, a small change to the hypothetical
platform produced a much larger group of cross-pressured moral liberals, and in this experiment, the
treatment effect was much larger among moral liberals.
In both studies, the largest treatment effects were found among those with the most
consistently extreme moral values preferences. This result dovetails with our analysis of self-reported
relative weights, which suggested that the most extreme moral conservatives and moral progressives
are more likely to report that they give greater weight to the moral values dimension.
The results of the survey experiments also dovetail with our classification of Democratic and
Republican voters into a two-dimensional issue space through the application of a supervised learning
model to several decades of survey data. While the survey experiment allowed us to examine the
realignment of electoral competition in response to the experimental manipulation of candidate
platforms, the survey data from the 1970s to the present allowed us some measure of external validity
by observing the realignment of partisan politics as the parties’ platforms on the social dimension
diverged over time. Not only did the dividing line between Democratic and Republican voters shift, but
as in the survey experiment, that shift appears to have been driven, at least initially, by those with the
most extreme preferences on the social dimension.
35
These findings are consistent with the theoretical literature on multi-dimensional politics that is
summarized in Miller and Schofield (2008). However, they are at odds with a large quantity of empirical
work in American politics that assumes a single dimension of partisan conflict. Questions about the
dimensionality of politics are unlikely to be solved via methodological debates about dimensionreduction techniques applied to survey or roll-call data. The simplest result in this paper—the difference
in voting behavior between bundled and unbundled treatment conditions—provides a strong indication
of multi-dimensionality that does not rely on the assumptions and judgment calls that are unavoidable
with such techniques.
These simple experimental results have potentially important implications for recent debates in
American politics. A key finding in the literature on polarization and ideological sorting is that over
recent decades, people with conservative issue preferences have become steadily more likely to identify
as Republicans, and those with progressive issue preferences have become more likely to identify as
Democrats. Less attention is given to the fact that ideological sorting has taken place exclusively on
issues related to moral values (Levendusky 2009). Economic preferences are just as powerful as
predictors of vote choice as in the 1960s. When the Democrats and Republicans came to be seen as
taking distinctive positions on issues related to moral values in the 1980s, cross-pressured moral
conservatives abandoned the Democrats. Likewise, cross-pressured moral progressives abandoned the
Republicans.
Since individuals with similar preference profiles are often clustered in geographic space, this
sorting of cross-pressured individuals can lead to new patterns of geographic segmentation, especially
since politics has become more nationalized and parties are finding it more difficult to credibly maintain
idiosyncratic local policy platforms. Rodden (2015) demonstrates a striking increase in the county-level
correlation between population density and democratic presidential voting, much of which can perhaps
36
be explained by a correlation between lower population density, religiosity, and conservative moral
values preferences. Rodden and Warshaw (2009) find that cross-pressured moral progressives are most
common in large cities and especially affluent suburbs, and cross-pressured moral conservatives are
most often found in rural areas. The former have become steadily more Democratic, and the latter more
Republican, since the introduction of the moral values issue dimension.
It may also be the case that the within-district ideological polarization documented by McCarty
et al (2015) has increased over time because of the introduction of divergent party platforms on moral
issues. Spatially heterogeneous electoral districts containing a small 19th century urban industrial
center—e.g. Lansing, MI or Fort Wayne, IN— and a surrounding rural periphery may have had very little
in the way of urban-rural political cleavage prior to the rise of moral values politics, whereas today the
ideological cleavage between urban and rural dwellers is very sharp.
Our findings also point to another possibility in districts containing clusters of cross-pressured
voters with extreme moral values preferences and/or high weights placed on those preferences:
incumbents can potentially amass a voting record on economic issues that is rather distant from, or
perhaps even incongruous with, the preference of the median voter in the district. Silicon Valley
Democrats can please their party and donors by voting for locally unpopular tax increases, and Southern
Republicans can do the same by voting for painful benefit cuts.
Finally, the introduction of the moral values dimension in a context where the perceptions of
party platforms are increasingly national can have profound impacts on political competition in the U.S.
states. Rodden and Warshaw (2009) demonstrate that there are large concentrations of Libertarians in
the Northeast and on the West Coast, and large concentrations of Christian Democrats in the Midwest
and especially the South. States with large concentrations of cross-pressured moral liberals, like
California, have seen a precipitous decline in the competitiveness of the Republican Party in the years
37
since the parties’ platforms on moral issues diverged. Likewise, the competitiveness of the Democratic
party has declined in Southern states with large concentrations of cross-pressured moral conservatives
(see Gelman et al 2008). Our results are consistent with an interpretation in which the introduction of a
policy dimension related to moral values has not given either party a long-term advantage in the
popular vote in presidential elections, but it has made life increasingly difficult for the Republican
leadership in states like California and the Democratic leadership in states like Arkansas.
In conclusion, the familiar assumption of unidimensionality remains useful in a number of
research settings, but it may stand in the way of progress in unraveling some of the largest unresolved
questions in a country with a large religious divide and a strict two-party system.
38
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40
Supporting information
1. American National Election Studies: Time Series Cumulative Data File
We use the cumulative file of the American National Election Studies (September 25, 2014 version) and
select the studies conducted on Presidential Election years between 1992 and 2012. The variables
included in the economic and moral issue scales are items that have been asked in most of the period
(at least six out of the eight waves) and that have at least moderate correlations with the other issues.16
Items included in the economic issue scale (reliability coefficient is 0.76):
VCF0806: Governmental or private health insurance plan (7-point scale)
VCF0809: Guaranteed jobs and income (7-point scale)
VCF0839: Government Services and Spending (7-point scale)
VCF0886: Federal Spending: Poor people (3-point scale)
VCF0887: Federal Spending: Child care (3-point scale)
VCF0890: Federal Spending: Public schools (3-point scale)
VCF0894: Federal Spending: Welfare programs (3-point scale)
VCF9049: Federal Spending: Social Security (3-point scale)
Items included in the moral issue scale (reliability coefficient is 0.76):
VCF0834: Women should have an equal role (7-point scale)
VCF0838: Abortion (4-point scale)
VCF0876a: Law against homosexual discrimination (4-point scale)
VCF0877a: Gays in the military (4-point scale)
VCF0878: Should Gays/Lesbians be able to adopt children (2-point scale)
VCF0851: Newer lifestyles contribute to society breakdown (5-point scale)
VCF0852: One should adjust moral views to changes (5-point scale)
VCF0853: More emphasis on traditional values (5-point scale)
VCF0854: Tolerance of different moral standards (5-point scale)
We extract the scores of the latent variables from the indicators using a standard structural equation
measurement model for latent traits. The correlations with the scores obtained when using other latent
variable extraction techniques range from 0.97 to 0.99. This approach is preferable to IRT because many
of the indicators are continuous while IRT is most commonly used and best suited for dichotomous or
other categorical variables. One common solution in similar situations is to dichotomize responses
(Tausanovitch and Warshaw 2013), but we refrain from doing this because the quality of attitudinal
measures is higher when using polytomous scales (Krosnick and Presser 2010; Saris and Gallhofer 2007).
We exclude 145 cases with missing values for all of the items included in one of the issue scales. The
model imputes the missing data based on the observed correlations between the items. When drawing
the svm plots, we drop 232 observations with very conservative issue positions of 2.5 standard
deviations above the mean in order to keep the axes similar in size and to avoid large areas of the plots
16
For instance, we exclude questions on spending on crime and science because they show very low correlations
with other items.
41
populated by a very sparse number of cases. The svm plots, which only include voters, draw on a total of
12,376 observations.
All the decisions are documented and can be consulted in the replication materials.
Socio-demographic and political characteristics of respondents in each quadrant in the ANES 2012
The following table examines the socio-demographic and attitudinal characteristics of respondents
classified in four quadrants according to their issue orientation using data from the 2012 ANES dataset.
Left-wing respondents have scores of economic and moral issue positions below the mean value in the
sample, right-wing respondents have issue positions above the mean in both, and Christian-Democrats
and Libertarians occupy the two off-diagonal quadrants.
Table A1: Characteristics of respondents in each quadrant
Age (in years)
Male (%)
Hispanic (%)
Black (%)
Low education (%)
Income<33 percentile (%)
North east (%)
North central (%)
South (%)
West (%)
Union member (%)
Never attends church (%)
Protestant (%)
Catholic (%)
Voted in 2012 (%)
If voted, for Republican (%)
N
Left-wing
45
44
13
19
39
38
18
22
35
25
9
54
26
22
71
10
2,006
Right-wing
52
54
7
3
40
22
15
23
40
22
9
30
41
22
80
87
1,642
ChristianDemocrats
48
45
18
23
62
48
14
19
46
21
9
27
40
20
62
33
1,134
Libertarians
45
47
8
5
30
21
22
23
32
24
10
58
25
24
73
47
1,122
Cross-pressured voters have distinct socio-demographic and political profiles. Christian Democrats are
more racially diverse than other groups, much less educated and poorer, and more likely to live in the
South. They are the group with the lowest turnout rate. They are similar in religious denomination and
church attendance to right-wing voters. Libertarians stand out for their high level of education and
infrequent church attendance. They have higher incomes than left-wing respondents and similar to
right-wing respondents.
42
2. General Social Survey: 1972-2012 Cross-Sectional Cumulative Data
We use the Cross-Sectional Cumulative Data (June 19, 2014 version) of the General Social Survey (GSS)
1972-2012 and select the studies conducted between 1977 and 2012. We pool together all waves asked
in the four years after each election.17 The variables included in the economic and moral issue scales are
items that have been asked in most years (for most variables in over 20 waves) and that have at least
moderate correlations with the other issues.
Items included in the economic issue scale (reliability coefficient is 0.73):
eqwlth: Government should reduce income differences (7-point scale)
natheal: Spending on health (3-point scale)
natcity: Spending on problems of big cities (3-point scale)
natenvir: Spending on environment (3-point scale)
natfare: Spending on welfare (3-point scale)
nateduc: Spending on education (3-point scale)
natsoc: Spending on social security (3-point scale)
conbus: Confidence in business (3-point scale)
conlabor: Confidence in labor (3-point scale)
helppoor: Government should improve standard of living (5-point scale)
helpnot: Government should do more (5-point scale)
helpsick: Government should help to pay for medical care (5-point scale)
helpblack: Government should aid blacks (5-point scale)
Items included in the moral issue scale (reliability coefficient is 0.69):
abortion: Additive score of seven questions about circumstances in which abortion is
justified (abdefect abnomore abhlth abpoor abrape absingle abany) (7-point scale)
fepol: Women are not suited for politics (2-point scale)
conclerg: Confidence in organized religion (3-point scale)
prayer: Bible prayer in public schools (2-point scale)
sexeduc: Sex education in public schools (2-point scale)
divlaw: Divorce laws (2-point scale)
premarsx: Sex before marriage wrong (4-point scale)
homosex: Homosexual sex relations wrong (4-point scale)
suicide1: Suicide if incurable disease (2-point scale)
Again, the scales were created using a standard structural equation measurement model. The GSS has a
complex ballot design with fixed and rotating modules, split ballots, and, since 1988, with the issue
questions spread across three different ballots. We do not include about 6000 cases with missing values
for all of the items included in one of the issue scales. We also drop 583 observations with very extreme
issue positions of 2.5 standard deviations above the mean on any of the scales. The svm plots only
include voters. This leaves us with 27,346 observations.
17
For instance, we pool responses to the 1977, 1978, 1979, and 1980 surveys which asked about vote choice in the
1976 presidential election and the 2010 and 2012 waves that asked about vote choice in the 2008 presidential
election. Note that at the time of writing the data asking about vote in the 2012 election had not been released.
43
3. The candidates experiment
Characteristics of the studies and the samples
The online studies, conducted in the US in June 2013 and July 2014, contained quotas by age, education,
and place of residence generated using census estimates. Hence, the distribution of these variables is
similar to the overall US population. In spite of this, the samples may differ from the population in
important respects. Table A2 compares the distribution of responses to variables that had the exact
same question wording in our surveys and in the pre- and post-election waves of the 2012 American
National Election Study.
Table A2: Comparison of selected questions of the online surveys with the 2012 Time Series ANES
ANES 2012 face-to-face
Unweighted
Weighted
ANES 2012 web
Unweighted
Weighted
SSI 2013
Unweighted
SSI 2014
Unweighted
Party identification
Democrat
46.8
34.6
38.1
36.1
39.8
40.7
Republican
17.3
24.9
27.6
29.4
25.2
25.1
Independent
33.8
37.2
31.2
31.1
31.8
30.1
Other party
2.2
3.3
3.1
3.5
3.2
3.2
Ideology
Extremely liberal
4.9
3.0
3.2
3.2
7.6
7.0
Liberal
14.1
13.1
11.3
10.4
14.3
14.0
Slightly liberal
13.1
11.4
11.7
11.8
11.2
8.4
Moderate
32.6
30.7
35.2
36.0
35.4
34.3
Slightly conservative
15.5
17.1
14.7
15.0
11.5
10.7
Conservative
16.1
20.1
20.0
19.1
14.6
14.1
Extremely conservative
3.9
4.7
3.9
4.6
5.4
11.4
Abortion self-placement
Should never be allowed
12.1
11.8
11.1
12.5
13.5
9.5
Rape, incest, or danger
27.9
27.6
27.2
27.7
31.0
27.0
For other reasons
15.9
17.5
15.1
14.6
15.6
15.1
Personal choice
44.2
43.0
46.6
45.2
39.9
48.5
Same-sex marriage
Allowed to marry
42.9
42.9
39.1
40.1
48.5
49.5
Civil unions
31.8
33.3
34.6
33.6
26.5
24.8
No legal recognition
25.3
23.8
26.3
26.3
25.0
25.7
Note: The table reports the distribution of responses for questions that had the exact same question wording in
the 2012 American National Election Study and in the online surveys conducted in June 2013 and July 2014.
The comparison suggests that the online samples, particularly the second, are more ideologically liberal
than the ANES samples. A left-wing bias is common in online samples. However, the differences are not
large in magnitude. In terms of party identification, the distribution of responses was similar to the
unweighted ANES responses and suggests that the samples are not unusual. The last survey was more
liberal on abortion and same-sex marriage.
In robustness checks, we attempted to address the ideology bias by weighting observations by reported
partisanship and past reported vote choice. We used the weighted full sample of the 2012 American
National Election Study (ANES) study to create the weights. The unweighted results we report in the
paper, however, never change significantly.
44
Generation of the economic and moral issue scales in the survey experiments
The economic and moral issue scales are the latent scores extracted from measurement models applied
to the following issue questions. We also fitted various alternative models with identical results. The
first experiment contained a larger number of issue questions, but the results do not change when using
scales that include those. We retain the shorter scales to maximize comparability. Higher values always
stand for morally conservative views.
Items included in the economic issue scale (reliabilities reported in the text):
- Spending on unemployment benefits (5-point scale)
- The government should reduce income differences (7-point scale)
- Raising taxes for the rich (5-point scale). The rich were defined as earning more than $250,000
per year in the first study and $100,000 per year in the second study.
Items included in the moral issue scale (reliabilities reported in the text):
- Abortion (4-point scale)
- Same-sex marriage (3-point scale)
- Adoption by same-sex couples (2-point question in the first study and modified 5-point question
in the second study)
The survey experiment
To illustrate how respondents encountered information about the candidates, we reproduce the
wording of the policy bundling condition in the first experiment.
We would like to know your opinion about two [four] candidates. They have similar platforms
on all major political issues except for the positions we describe below. The description is
general, and is not about candidates from a specific party.
Which candidate do you prefer?
 Candidate A
 Candidate B
Figure A1: Information about the candidates in the “policy bundling” treatment
The relative importance of issues across issue positions
45
Table A3 extends the results presented in the section “The relative importance of issues for moral
moderates and extremists” in two ways. First, while the paper focuses on the correlation between alpha
and moral issues, here we also examine if economic issue positions predict the self-reported relative
importance of issues. Second, we present a multivariate analysis instead of a simple bivariate analysis in
order to control for characteristics that may affect the relative importance of each dimension such as
socio-economic status or geographic location.
We model the self-reported relative importance of issues (where higher values stand for a larger relative
importance of moral issues) as a function of moral values in model 1 and include a squared term in order
to directly test the idea that both groups of moral extremists attach more relative importance to moral
issues. The results replicate the u-shaped pattern found in the bivariate analyses and are robust to the
inclusion of controls for economic issue positions (in model 3), individual-level characteristics (model 4),
and state fixed-effects (model 5).
Model 2 assesses the relationship between relative importance and economic conservatism, and finds a
negative correlation. However, this relationship is not statistically significant when controlling for
respondents’ position on moral issues and becomes even smaller in size when adding controls. This
finding suggests that the relative importance of issues is constant for economic extremists and
moderates. This is relevant because throughout the analysis we assume away the correlation between
alpha and economic issue positions. Table A3 suggests that this is a reasonable assumption.
Table A3: The relative importance of issues across moral and economic issue positions
Model 1
Model 2
Model 3
Model 4
Model 5
Moral issues (conservative)
-0.23***
-0.20***
-0.19***
-0.19***
(0.04)
(0.05)
(0.05)
(0.05)
Moral issues squared
0.36***
0.35***
0.34***
0.33***
(0.05)
(0.05)
(0.05)
(0.05)
Economic issues (conservative)
-0.11**
-0.06
-0.04
-0.04
(0.04)
(0.04)
(0.04)
(0.05)
Economic issues squared
-0.01
-0.01
0.00
-0.00
(0.03)
(0.03)
(0.03)
(0.03)
Constant
3.03***
3.40***
3.05***
2.92***
2.41***
(0.06)
(0.05)
(0.07)
(0.53)
(0.62)
Individual controls
No
No
No
Yes
Yes
State-level fixed effects
No
No
No
No
Yes
R-Squared
0.063
0.008
0.066
0.121
0.189
Obs.
908
908
908
907
907
+ p<0.1, * p<0.05, ** p<0.01, *** p<0.001. Individual level controls are: age, sex, education, income, race, Hispanic
origin, marital status, home ownership, religious denomination, and church attendance.
46